1. Technical Field
The present invention relates to an antistatic coating composition. More particularly, the present invention relates to an antistatic coating composition comprising an ionic liquid. An antistatic film formed of the composition of the present invention has high pencil hardness and low surface resistivity.
2. Description of Related Art
In recent years, liquid crystal display (LCD) and plasma display have been drawing more attention to the industry and become more popular to customers with the improvement of method for manufacturing semiconductor and optical elements. For inhibiting the surface of a display from scratching by external force or electrostatically adhering air dust, a hard coating with antistatisticity is provided to the surface of the display. The hard coating with antistaticity can also be applied to the articles which need scratch-proofing and antistaticity, such as, sun glasses, camera lenses and car windows in order to avoid dust and debris adhered thereon due to the friction.
Several methods have been proposed to provide antistatic function to an article, especially to a film, including: by adding carbon black, metal powder, conductivity metal oxide, surfactant or ionic liquid into a composition for forming the article; or by disposing an antistatic layer comprising conductive fillers or surfactant on the surface of the article.
The approaches mentioned above have various disadvantages. For example, it is known that the addition of metal or non-metal conductive particles to antistatic coating composition will decrease surface resistivity and thus enhance the conductivity of the film formed by the coating composition. However, the addition of particles into the film-forming composition will affect optical characteristic of the film formed thereof, such as lower the transparency thereof and thus the optical products with the film will be adversely affected. Furthermore, this composition is insusceptible to be cured completely during a curing treatment and thus, the surface hardness of the film formed by the said composition does not reach the required level. Another method is proposed by adding a surfactant or an ionic liquid to a composition for forming an antistatic layer. The duration of antistaticity provided by the layer formed by the composition comprising a surfactant or an ionic liquid is easily to be damaged because the antistaticity of the layer is susceptible to be affected by environmental humidity i.e., for example, the surfactant or the ionic liquid in the antistatic layer is easily to be stripped by being wiped with water or alcohols or by being subject to external friction, or the antistatic layer is hazed to lower the light transmittance. It is also suggested a multi-layer structure by coating to manufacture an antistatic film. However, an antistatic film of multi-layer structure is costly in manufacturing process because of the multi-coating process. Moreover, metal oxides such as indium tin oxide (ITO) which is transparency and conductive by electron transferring meet the requirements mentioned above, but a sputtering system is needed in the manufacturing process, which will increase manufacturing cost and make the manufacturing process more complicated. In additions, the flexibility of a coating of inorganic metal oxides is low and thus, will easily peel from the substrate on which the coating is formed, and result in the conductive thereof. Additionally, the conformity between a coating of metal oxides and an organic substrate is low, it may cause the coating peel and make the transparency to decrease.
There is a need to improve the disadvantages mentioned above. The present invention is to provide an antistatic coating composition and an antistatic film formed therefrom to alleviate the aforesaid disadvantages of the prior art. The antistatic coating composition according to the present invention comprises a hard coating solution and an antistatic solution. An antistatic film formed by curing the antistatic coating composition has high hardness and high transmittance without sacrificing the quality of the optical production, and provide an excellent weather resistance without being affected by environmental impact.